Buffer hasArray() methods in Java with Examples

The hasArray() method of java.nio.Buffer class is used to tell whether or not this buffer is backed by an accessible array. If this method returns true then the array and arrayOffset() methods may safely be invoked. Syntax:

public abstract boolean hasArray()

Returns: This method will return true if, and only if, this buffer is backed by an array and is not read-only. Else it returns false. Below are the examples to illustrate the hasArray() method: Examples 1: When the buffer is backed by an array 

Java

// Java program to demonstrate
// hasArray() method

import java.nio.*;
import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // Declaring the capacity of the ByteBuffer
        int capacity = 10;

        // Creating the ByteBuffer
        try {

            // creating object of bytebuffer
            // and allocating size capacity
            ByteBuffer bb = ByteBuffer.allocate(capacity);

            // putting the value in bytebuffer
            bb.put((byte)10);
            bb.put((byte)20);
            bb.rewind();

            // Typecast bytebuffer to Buffer
            Buffer buffer = (Buffer)bb;

            // checking buffer is backed by array or not
            boolean isArray = buffer.hasArray();

            // checking if else condition
            if (isArray)
                System.out.println("buffer is"
                                   + " backed by array");
            else
                System.out.println("buffer is"
                                   + " not backed by any array");
        }

        catch (IllegalArgumentException e) {
            System.out.println("IllegalArgumentException catched");
        }

        catch (ReadOnlyBufferException e) {
            System.out.println("ReadOnlyBufferException catched");
        }
    }
}

Output:

buffer is backed by array

Examples 2: When the buffer is not backed by an array 

Java

// Java program to demonstrate
// hasArray() method

import java.nio.*;
import java.util.*;

public class GFG {

    public static void main(String[] args)
    {

        // Declaring the capacity of the ByteBuffer
        int capacity = 10;

        // Creating the ByteBuffer
        try {

            // creating object of ByteBuffer
            // and allocating size capacity
            ByteBuffer bb = ByteBuffer.allocate(capacity);

            // putting the value in ByteBuffer
            bb.put((byte)8.56F);
            bb.put((byte)10);
            bb.rewind();

            // Creating a read-only copy of ByteBuffer
            // using asReadOnlyBuffer() method
            ByteBuffer bb1 = bb.asReadOnlyBuffer();

            // Typecast read-only ByteBuffer to read-only buffer
            Buffer buffer = (Buffer)bb1;

            // checking buffer is backed by array or not
            boolean isArray = buffer.hasArray();

            // checking if else condition
            if (isArray)
                System.out.println("buffer is"
                                   + " backed by array");
            else
                System.out.println("buffer is"
                                   + " not backed by any array");
        }

        catch (IllegalArgumentException e) {
            System.out.println("IllegalArgumentException catched");
        }

        catch (ReadOnlyBufferException e) {
            System.out.println("ReadOnlyBufferException catched");
        }
    }
}

Output:

buffer is not backed by any array

Reference: https://docs.oracle.com/javase/9/docs/api/java/nio/Buffer.html#hasArray–